In general, it is known to provide a pair of members for shearing a tree, at least one of which is movable in a manner so as to determine a spherical cut of a tree. See, for example, U.S. Pat. No. 3,540,501; U.S. Pat. No. 3,854,510; and Canadian Pat. Nos. 873,685, 840,776 and 975,260. In each of these patents, the two elements utilized for the shearing of a tree (i.e., two-blade elements, or a blade element and anvil) are pivotally connected by means of a single pivot pin, which must absorb a relatively great amount of the loads placed on the two elements during the shearing operation. It will be understood that it is highly desirable to carry the loads placed on the two elements in a more efficient manner meanwhile still achieving the spherical tree cut described above to minimize tree damage during such cut.
Of more general interest in this area are U.S. Pat. No. 3,857,425, disclosing a spherical saw-blade, movable in a pendulous motion, U.S. Pat. No. 1,509,994, disclosing a pair of cutting elements of generally cylindrical configuration, U.S. Pat. No. 3,837,382, which discloses a system including a cutting blade of generally cylindrical configuration, U.S. Pat. No. 3,835,901, which discloses a rotary saw ring as a cutting element, Canadian Pat. No. 896,322, which discloses a pair of trough-shaped blades, movable toward and away from each other, and Canadian Pat. No. 975,661, disclosing cutting bits in the shape of part of a double cone.